It has frequently been observed that like tends to marry like with respect to many social, economic, and demographic characteristics. However, the extent to which marriages are homogamous has not been accurately measured, nor is there an adequate understanding of why many marriages are heterogamous with respect to those characteristics. The theoretical perspective underlying the proposed research is that those marrying seek to maximize their rewards from marriage, but that in choosing a marriage partner males are more likely to emphasize non-economic characteristics and females economic characteristics. Three major study hypotheses follow from those assumptions: (1) that there is a strong tendency toward homogamy by age, race, ethnicity, education, and marriage order; (2) that deviations from homogamy can be interpreted as reflecting the different emphases of males and females, and that there will be some exchanges involving economic characteristics of the groom (such as education) and non-economic characteristics of the bride (such as age); and (3) that the 1970-1980 movement toward greater equality by sex and race will be reflected in a reduction in deviations from homogamy by education, and in an increase in interracial marriage. The study hypotheses will be examined using 1970 and 1980 vital statistics marriage data and Census public use data for seven U.S. states. A regression format will be employed, with the dependent variable a composition-independent measure of marriage, and the independent variables functions of the bride and groom's age, race/ethnicity, education, and marriage order. The results will increase present understanding of "who marries whom", and shed light on how marriage behavior is responding to social change.